We've all heard about the six signs of an impending stall that have been
drilled into us by some flight instructors. They are extremely important.
In case you have forgotten them they are:

1. Excessive back stick pressure

2. Nose high attitude

3. Low airspeed

4. Quietness

5. Mushy controls

6. Shudder or buffetting

I do not believe each of these signs is of equal importance. Futhermore,
some of these signs are causes while others are results. To truely identify
what causes a stall (and therefore how to avoid one) we must separate the
cause signs from the results signs.

The number 1 sign, "Excessive back stick pressure", is a cause
sign but is very hard to get across to a student. What is excessive?
1 pound, 2 pounds, 10 pounds? What about the trim on the plane? If it
is trimmed wrong could that cause excessive back stick pressure without
being close to a stall? In other words excessive back stick pressure could
exist and one is not close or getting close to a stall. Therefore, I pretty
much discount this cause when I am teaching stall awareness/avoidance.
It can confuse the student more than help.

The number 2 sign, "Nose high attitude" is a cause of stalls
and will always be there when a sailplane stalls. It is unmistakable and
it is easy to teach. Couple the teaching of this sign with the hazards
of skidding the sailplane and, if followed, a student will never stall a
sailplane. This sign is by far the most important in teaching stall awareness/avoidance.
If students learn to keep the nose below the horizon they are well on their
way to never inadvertently stalling.

The number 3 sign, "low airspeed", goes hand in hand with
"Nose high attitude" and is a good indicator for students. However,
it is really a result of " nose high attitude". With students
it is the main result sign that will help a student avoid stalls. That
is, if a student keeps his airspeed well above the published stall speed
he will not and, as a matter of fact, can not stall the sailplane. The
old adage that a plane can stall at any attitude at any airspeed is, in
the real world, simply not correct (unless the student jerks back on the
stick as fast and as hard as he can and students just don't do that).

The number 4 sign, "Quietness" is another result sign and is
not a cause of stalls. Different sailplanes have different levels of noise.
I certainly do not want students to first recognize the beginning of a
stall by quietness. It is much too late at this stage.

The number 5 sign, "Mushy Controls", is another result sign
of impending stalls. Similar to "Quietness" it is a sign I never
want my students to get to. If they pay attention to "nose high attitude"
and "airspeed" this number 5 will not happen. Remember, we teach
stall awareness/avoidance.

The number 6 sign, "shutter or buffeting", is also a result
sign not a cause sign. Furthermore, this sign occurs in other situations.
For instance, upon release from the tow plane I have had students get hit
by the prop wash of the towplane and push forward on the stick thinking
they are stalling. NOT!! On the other hand some sailplane just stall without
a hint of a shutter or buffet. So number six sign is not one of the more
important one.

In summary, two signs stand head and shoulders above the rest to be
used for stall awareness/avoidance. They are:

NOSE HIGH ATTITUDE (a cause)

&

LOW AIRSPEED (a result)

There is however, one other point that needs to be reemphasized. SKIDDING
TURNS drastically increase the stall speed of a sailplane. The more you
skid a turn the LESS nose high attitude it takes to stall and this stall
will occur at a higher airspeed.